Visiting Saturn: 40 Years Since Pioneer 11's Mission to Giant Ringed PlanetBy Ben Evans, on September 1st, 2019
(...) Early in December 1974, after 21 months traveling through deep space, Pioneer 11 became the second spacecraft in history to successfully reach and study Jupiter. Its next mission would truly be an adventure into the Solar System’s uncharted depths. And with the unknown came problems. They manifested themselves in the form of spurious spacecraft commands, which went on for several months and could not be attributed to radiation. It turned out that Pioneer 11’s asteroid/meteoroid detector—a non-imaging tool designed to track particles from dust-size up to larger objects—had sustained radiation damage and was the source of the problem. It was correspondingly shut down, but during the process to identify the problem the spacecraft’s healthy plasma analyzer was also turned off. When commanded back on again, it came alive, but for a while refused to provide data. It was just another reminder that Pioneer 11 was voyaging into the unknown.
There existed two main proposals to observe Saturn at close range, which called for Pioneer 11 to daringly pass inside the ring-plane or, more conservatively, outside. NASA management opted for the more conservative option, keenly aware that Pioneer’s data would prove critically important for the upcoming Voyager missions.
Humanity’s first-ever visit to Saturn would clearly be a momentous event, especially for those retirees who had worked on the project earlier in its conception. Six key retirees, known affectionately as the “over-the-hill gang”, returned to work for this critical period.
Late in July 1979, the spacecraft’s campaign to observe Saturn from afar began in earnest. NASA managers had selected a flight path which would provide a pathfinder for the twin Voyager probes—which, it was hoped, would conduct flybys of all four gas giants during their “Grand Tour” of the outer Solar System—and on 29 August Pioneer 11 began several weeks of close-range observations of the Saturnian system. Early that morning, it passed the strange, two-toned moon Iapetus, followed by tiny Phoebe a few hours later. Two days later, the spacecraft swept within 414,000 miles (666,000 km) of Hyperion, before embarking on its close passage of Saturn on 1 September.
That day’s events commenced with encounters with the moons Epimetheus, Atlas, Mimas—characterized by its vast Herschel crater—and Dione, before achieving a closest approach to Saturn of 12,795 miles (20,591 km) at 11:29:34 a.m. EDT. Over the next few hours, Pioneer 11 passed the moons Janus, Tethys, Enceladus, Calypson and Rhea, before making a distant flyby of Saturn’s giant, planet-sized satellite Titan at 1 p.m. EDT on 2 September. Yet even those distant observations showed that smog-enshrouded Titan was likely far too cold to support life.
Several more weeks of distant observations were conducted from afar and by the beginning of October 1979 Pioneer 11’s focus on Saturn ended, as the ringed planet diminished and size and steadily disappeared from view. So began the Pioneer Interstellar Mission to send the spacecraft out of the Solar System forever. (...)
https://www.americaspace.com/2019/09/01/visiting-saturn-40-years-since-pioneer-11s-mission-to-giant-ringed-planet/
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